An analysis of nationally representative prescription data revealed that nearly half of people taking tenofovir/emtricitabine (Truvada) for pre-exposure prophylaxis (PrEP) are women, according to a poster presented at the 53rd Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC 2013) this week in Denver. The study also found that people using Truvada for HIV prevention were more likely to be under age 25 than those using it for treatment.

A U.S. survey of the prescribing of Truvadato HIV negative people as PrEP has found that, when participants in clinical trials and demonstration projects are excluded, PrEP recipients are more likely to live in the southern states and are more likely to be female than people receiving Truvada for HIV treatment.

The survey found that prescriptions for PrEP represented perhaps 1% of all Truvada prescriptions, though use has grown slowly. However, the majority of PrEP in the U.S. is still being prescribed in the context of clinical trials; this survey represents prescribing outside trials, by individual doctors in a variety of healthcare settings.

The study only used prescription information from 55% of all U.S. pharmacies, so the true figure for PrEP prescriptions will be somewhat higher. The figures were derived by looking at all prescriptions for Truvada from the pharmacies surveyed and sequentially eliminating certain categories of patients, so the remainder were all deemed to be PrEP prescriptions:

All prescriptions that included other antiretrovirals or hepatitis B drugs;

All patients diagnosed with HIV or with any diagnosis of an AIDS-related opportunistic infection;

All patients with chronic hepatitis B;

All prescriptions for post-exposure prophylaxis (PEP).

The U.S. Food and Drug Administration (FDA) approved the use of Truvada as PrEP in July 2012. Although -- so far at least -- its use has only grown slowly, it began to gather speed even before the FDA approval.

The survey found prescriptions for PrEP made out to 150 individuals in 2011. In 2012 Truvada PrEP was prescribed to 1274 individuals, but only slightly more than half of these (681) were prescribed after FDA approval. In the first quarter of 2013, 350 more individuals were prescribed PrEP, implying a total of at least 2000 for the whole year. However with Truvada being one of the most frequently prescribed antiretroviral drugs for HIV treatment, this probably only represents 1%-2%, at most, of all Truvada prescribing in the U.S.

A total of 620 healthcare professionals (37% of all those surveyed) were found to have prescribed PrEP at least once during the survey period, from January 2011 through March 2013.

The median age of PrEP recipients was 37 years and there was a trend over time for PrEP recipients to get younger (3% of recipients were under 25 in 2011 compared with 14% overall).

PrEP was most likely to be prescribed by family practitioners (i.e., GPs) in the southern states, and primary care prescribing was also more common on the west coast. In areas other than the south, Truvada PrEP was most likely to be prescribed by internal medicine practitioners (i.e., generalist physicians rather than the infectious disease specialists who would normally treat HIV) and in the midwest it was often prescribed by emergency doctors too. However, all broad medical specialties prescribed some Truvada for PrEP, including nurse practitioners, who prescribed about 1 in 10 courses.

When compared to people receiving Truvada for HIV treatment, PrEP recipients were 1.8 times more likely to be women, 1.4 times more likely to be under 24 years old, 1.4 times more likely to be from the southern states, and 3.8 times more likely to have Truvada prescribed by someone who was not an infectious diseases specialist.

In is important to emphasize that a high proportion of Truvada PrEP in the U.S. is currently being prescribed in the context of a clinical trial or demonstration project. In California alone, the state HIV/AIDS research program plans to enroll 4000 people in PrEP implementation trials. These individuals may be more likely to be gay men attending larger sexual health centers.